1. Field of the Invention
The present invention relates generally to spinal fixation systems and in particular to spinal fixation systems including a selectively applied bone growth promoting agent.
2. Description of Related Art
Spinal fusion implants have been previously proposed and utilized in cervical thorastic, lumbar and sacral regions. Currently, these fixation systems are utilized to hold various segments of the spine together allowing for fusion to occur. These implant systems include plates, screws, rods, hooks and cables utilized for the anterior, posterior as well as lateral portions of the spine. All these systems utilize inert materials, mostly metal, to fix the bone and allow the natural process of healing to occur. None of these systems in use actually encourage the growth of bone to facilitate the fusion or healing. Furthermore, none of these systems utilize healing processes to heal to the actual implant by providing a re-bar effect and better fixation.
One type of spinal fusion implant, the threaded spinal implant (commonly referred to as a spinal screw), may include provisions for promoting bone growth through the cage. This type of prosthesis is disclosed in Michelson (U.S. Pat. No. 6,264,656), the entirety of which is incorporated by reference. The threaded spinal implant is inserted between two adjacent vertebrae and is incorporated into the fusion of the bone along this portion of the spine.
Brantigan (U.S. Pat. No. 4,834,757) discloses plugs, used as spinal fusion implants, the entirety of which is incorporated by reference. The plugs are rectangular with tapered front ends and tool receiving rear ends. Generally, the plugs may be used in a similar manner to the spinal screws of Michelson. As with the spinal screws, the plugs may be inserted between adjacent vertebrae. The plugs may include nubs that behave like teeth, countering any tendency for the plugs to slip between the vertebrae.
While the related art teaches various forms of spinal fusion implants, there are many shortcomings. Related art prostheses lack selectively applied bone growth promoting treatments. The prior art does not teach the selective application of the variety of known bone growth promoting treatments. There is therefore a need in the art for prostheses that incorporate selectively applied bone growth promoting treatments.